The "professional post-deleting", as it's come to be called, is a way of removing negative press and reviews from websites. The deletion is a major problem in China, but cross referencing a record of original posts with the deletions its employees make has allowed Baidu to identify the culprits. The company told The Global Times:

"Baidu has fired the four. If we discover such cases, we will severely punish staff. Baidu will close the loopholes by strengthening management to maintain order in our communication platform."

The Global Times points out that payments for post deletion can range from around $150 to delete a single forum post, $450 to delete a news story—a news story!—and up to $30,000 a year for what's referred to as a long-term "maintenance service", which sees any negative mentions of a company deleted immediately.

So, next time you rip into the irony of Google "don't be evil" policy, spare a thought for the Chinese. [WSJ and Global Times via Verge]